powerpc/pasemi: Remove obsoleted declaration for pas_pci_irq_fixup()

The pas_pci_irq_fixup() have been removed since
commit 771f7404 ("pasemi_mac: Move the IRQ mapping from the
PCI layer to the driver"), and now it is useless, so remove it.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240822130609.786431-4-cuigaosheng1@huawei.com